Steps to reproduce:

1. Research all skills in the TechPriest tree
2. Take an armor or 2-hand weapon for forging
3.  Drill 6 sockets there

Expected result:

The entire procedure costs exactly as shown, 1008.75k credits in total:
$ echo '15 + 56.25 + 112.5 + 187.5 + 262.5 + 375' | bc
1008.75

Actual result:
It costs 1.8 times more, 7409k - 5592k = 1817k as shown in the video below.
Additionally: the similar issue occurs with any other socket-ready item, regardless of the number of maximum sockets: 2 / 3 / 4 / 6

Note:
this bug could be related to

• either interface (incorrect sum displaying)
• or calculations (displayed sums are right, but actual costs are incorrectly processed at the backend side).

Environment / experience:

1. Game nickname: unixhorn
2. PS-4
3. The latest game version at the time of reporting
4. Non-seasonal game

Customer impact:

• High-level, hardcore players: annoying but manageable due to their high income from complex missions
• Novices and casual players: critical, as those guys typically might have limited budgets for techpriest operations, thus could be very disappointed of "shown VS real" prices => retention rate / NPS / CSI suffer.

Desirable compensation:

• P&L analysis: having 5 100lvl characters, forged >= 15 6-socket items for each one in average, 5*15*0.8m = 60m losses. Plus many 2/3/4-socket items, can't count then exactly. To proof the approx.number, can show my characters' inventory.
• Conclusion: it looks fair to ask for 80mln credits compensation.

Video proof: